Chanita Chantarasukon,1 Suparerk Tukkeeree,1 and Jeff Rohrer2
1
Thermo Fisher Scientific, Bangkok, Thailand; 2Thermo Fisher Scientific, Sunnyvale, CA USA
Appli cat i on N ote 1 0 5 3
Determination of Dissolved Manganese
in Lithium/Manganese Oxide
Battery Electrolyte
Key Words
Lithium-Ion Battery, Cathode, Dionex IonPac CS12A Column,
Reagent-Free Ion Chromatography System
Introduction
Lithium-ion batteries are widely used in products such as
portable consumer electronic devices and electric vehicles.
Many different materials are used to make the cathode
in lithium batteries, including those that are manganese-,
cobalt-, and nickel-based. Lithium-ion batteries that are
manganese-based are more environmentally friendly, have
a good safety record, and can be made at a lower cost;
however, they have a shorter lifetime than other types of
lithium-ion batteries. One of the reported causes of
lifetime loss is the dissolution of manganese from
the cathode into the electrolyte during cycling (i.e.,
charging/discharging). Lithium/lithium manganese
oxide (Li/LiMn2O4) is a type of battery that has a
manganese-based cathode.
In Thermo Scientific Application Note (AN) 258, ion
chromatography (IC) was applied to determine the anions
tetrafluoroborate, perchlorate, and hexafluorophosphate
in a simulated electrolyte solution for lithium-ion
batteries.1 AN 258 used a Reagent-Free™ IC (RFIC™)
system, and it is also possible to use an RFIC system to
determine manganese in a simulated electrolyte solution
for lithium-ion batteries. There is one report of an IC
method that uses manually prepared eluents and direct
conductivity detection to determine dissolved manganese
in the electrolyte of a Li/LiMn2O4 battery.2 However, that
method has poor sensitivity, which is inherent with direct
conductivity detection. Even with a three-component
(tartaric acid, dipicolinic acid, and ascorbic acid) mobile
phase, the manganese peak exhibits extreme tailing on the
chosen column. A better IC cation column will improve
peak shape and therefore improve integration precision
and method accuracy, while suppressed conductivity
detection will improve method sensitivity.
The work shown here uses an RFIC system with
suppressed conductivity detection to quantify dissolved
manganese in the simulated electrolyte of a Li/LiMn2O4
battery. The method uses the Thermo Scientific™ Dionex™
IonPac™ CS12A column set, which was designed to deliver
good peak shapes for cations such as manganese(II)
(Mn2+), with a simple methanesulfonic acid (MSA) eluent
produced by an eluent generator. The combination of the
RFIC system and a quality IC column yields a method
that is sensitive, accurate, reproducible, and easy to
execute, requiring only the addition of deionized water to
the RFIC system.
Goal
To develop an IC method that accurately determines
dissolved manganese in the electrolyte of a Li/LiMn2O4
battery using an RFIC system
2
Equipment
Sample Preparation
• Thermo Scientific Dionex ICS-2100 Integrated
Preparation of a Simulated Sample
Prepare 1.12 M of LiPF6 and 2 wt % of vinylene
carbonate in the mixture of ethylene carbonate and ethyl
methyl carbonate by placing 1.7 g of LiPF6 and 0.2 g of
vinylene carbonate in a 10 mL volumetric flask; dissolve,
then bring to volume with the mixture of ethylene
carbonate and ethyl methyl carbonate. Prepare a 1 to 50
dilution of this simulated sample using DI water prior to
injection. This is the same dilution used in the
published method.2
RFIC system,* including a Thermo Scientific Dionex
AS-AP Autosampler
• Thermo Scientific™ Dionex™ Chromeleon™
Chromatography Data System (CDS) software
version 6.80, SR9 or higher
*Any Thermo Scientific RFIC system may be used.
Reagents and Standards
• Deionized (DI) water (H2O), Type I reagent grade,
18 MΩ-cm resistivity or better
• Lithium Hexafluorophosphate (LiPF6), 98%
(Fisher Scientific P/N 21324-40-3)
Spiked Sample Simulation
Prepare 5 mg/L of manganese, 1.12 M of LiPF6, and
2 wt % of vinylene carbonate in the mixture of ethylene
carbonate and ethyl methyl carbonate by placing 1.7 g
of LiPF6, 0.2 g of vinylene carbonate, and 50 µL of
1000 mg/L manganese stock standard solution in a 10 mL
volumetric flask; dissolve, then bring to volume with the
mixture of ethylene carbonate and ethyl methyl carbonate.
Prepare a 1 to 50 dilution of this spiked simulated sample
using DI water prior to injection.
• Manganese(II) Sulfate, Monohydrate (MnSO4.H2O)
(Fisher Scientific P/N 10034-96-5)
Chromatographic Conditions
• Ethylene Carbonate (C3H4O3), 99%
(Fisher Scientific P/N 50-700-5617)
• Ethyl Methyl Carbonate (C4H8O3), 99%
(Sigma-Aldrich® P/N 754935)
• Vinylene Carbonate (C3H2O3), 97%
(Fisher Scientific P/N 50-751-1840)
Preparation of Solutions and Reagents
Mixture of Ethylene Carbonate and Ethyl Methyl
Carbonate, 1:1 (w/v)
Dissolve 10 g of ethylene carbonate in 10 mL of ethyl
methyl carbonate.
Manganese Stock Standard Solution, 1000 mg/L
Place 0.308 g of manganese(II) sulfate monohydrate in a
100 mL volumetric flask, dissolve in DI water, bring to
volume with DI water, and mix.
Working standard solution
Add the appropriate volumes of 1000 mg/L manganese
stock standard solution into separate 100 mL volumetric
flasks, bring to volume with DI water, and mix. The
volumes of manganese stock standard solution used for
the preparation of working standard solutions are shown
in Table 1.
Columns:
Dionex IonPac CG12A Guard, 4 × 50 mm
(P/N 046074)
Dionex IonPac CS12A Analytical, 4 × 250 mm
(P/N 046073)
Eluent Source:
Thermo Scientific Dionex EGC III MSA
Eluent Generator Cartridge (P/N 074535)
with Thermo Scientific Dionex CR-CTC II
Continuously Regenerated Cation Trap Column
(P/N 066262)
Eluent Concentration: 20 mM MSA
Flow Rate:
1.0 mL/min
Inj. Volume:
20 µL
Temperature:
35 °C
Detection:
Suppressed Conductivity, Thermo Scientific™
Dionex™ CSRS™ 300 Cation Self-Regenerating
Suppressor, 4 mm (P/N 064556), Recycle
Mode, Current 60 mA
Total Conductivity:
Table 1. Preparation of working standards.
Level
Volume of Manganese Stock
Solution (1000 mg/L) Used for
a 100 mL Preparation (mL)
Concentration
(mg/L)
1
0.010
0.10
2
0.020
0.20
3
0.040
0.40
4
0.080
0.80
5
0.100
1.00
~0.34 µS
3
Table 2. Working standard concentrations and calibration results.
Analyte
Concentration (mg/L)
Calibration Results
Level 1
Level 2
Level 3
Level 4
Level 5
Points
r2
Offset
Slope
0.1
0.2
0.4
0.8
1.0
15
0.9997
-0.0046
0.1617
Manganese
Results and Discussion
Separation
Manganese is a divalent cation that can be separated from
six common cations using the Dionex IonPac CS12A
column set with isocratic elution. As shown in Figure 1,
manganese is well separated from the other common
divalent cations—magnesium and calcium—using a
20 mM MSA eluent. Figure 1 also shows that manganese
is well resolved from other common cations. Note the
good peak shape for manganese and the other cations.
The MSA eluent is automatically produced by pumping
DI water through the eluent generator cartridge with the
concentration controlled by Chromeleon CDS software.
Columns:
Method Calibration
The method was calibrated before sample analysis using
five concentrations of manganese ranging from 0.1 to
1.0 mg/L. The method showed a linear relationship
between analyte concentration and peak area of
manganese. The coefficient of determination (r2) for the
line was 0.9997. Figure 2 shows the overlay of
chromatograms of the working (calibration) standards,
and Table 2 shows the concentrations of the working
standards and the calibration result. Note that a 20 µL
injection of the 0.1 mg/L standard produced a peak of
significant size and good peak shape, whereas the
nonsuppressed method in Reference 2 produced a small
tailing peak for a 1 mg/L standard (though only a 10 µL
injection). This highlights the expected sensitivity benefit
of using suppressed rather than nonsuppressed
conductivity detection.
Dionex IonPac CS12A Guard, 4 × 50 mm
Dionex IonPac CG12A Analytical, 4 × 250 mm
Eluent Source: Dionex EGC III MSA Cartridge with Dionex CR-CTC Column
Eluent:
20 mM MSA
Flow Rate:
1.0 mL/min
Inj. Volume: 20 µL
Temperature: 35 °C
Detection:
Suppressed Conductivity, Dionex CSRS 300 Suppressor,
4 mm, Recycle mode, Current 60 mA
Sample:
Standard Mixture
Columns:
Peaks:
Peak:
1. Lithium
2. Sodium
3. Ammonium
4. Potassium
5. Magnesium
6. Manganese
7. Calcium
4
1.0 mg/L
1.0
1.0
1.0
1.0
1.0
1.0
Dionex IonPac CS12A Guard, 4 × 50 mm
Dionex IonPac CG12A Analytical, 4 × 250 mm
Eluent Source: Dionex EGC III MSA Cartridge with Dionex CR-CTC Column
Eluent:
20 mM MSA
Flow Rate:
1.0 mL/min
Inj. Volume: 20 µL
Temperature: 35 °C
Detection:
Suppressed Conductivity, Dionex CSRS 300 Suppressor,
4 mm, Recycle mode, Current 60 mA
Sample:
Calibration Standard
1. Manganese
0.1, 0.2, 0.4, 0.8, and 1.0 mg/L
0.35
1
1
µS
µS
2
3
5
4
6
7
0
0
-0.5
-0.05
0
2.5
5
7.5
10
12.5
15
Minutes
Figure 1. Chromatogram of a standard containing six common cations
and manganese.
0 1
3
5
7
9
11
13
Minutes
Figure 2. Overlay of chromatograms of the calibration standards.
15
Figure 3 shows the overlay of chromatograms of the
simulated and spiked simulated samples. Note that the
magnesium and calcium peaks—eluting before and after
manganese, respectively—do not interfere with the
quantification of manganese. Overall, the results indicate
that this is an accurate and reproducible method for
determining manganese in Li/LiMn2O4 battery electrolyte.
Columns:
Dionex IonPac CS12A Guard, 4 × 50 mm
Dionex IonPac CG12A Analytical, 4 × 250 mm
Eluent Source: Dionex EGC III MSA Cartridge with Dionex CR-CTC Column
Eluent:
20 mM MSA
Flow Rate:
1.0 mL/min
Inj. Volume: 20 µL
Temperature: 35 °C
Detection:
Suppressed Conductivity, Dionex CSRS 300 Suppressor,
4 mm, Recycle mode, Current 60 mA
Samples:
Sample
Spiked Sample
Peak:
1. Manganese
0.1033 mg/L
0.3
µS
Conclusion
This study demonstrates an accurate and reproducible IC
method that uses suppressed conductivity detection to
determine manganese in the simulated electrolyte of a
Li/LiMn2O4 battery. The method uses an RFIC system and
requires only 15 min per analysis with a simple isocratic
separation using an MSA eluent. The eluent is produced
by an eluent generator to preclude the labor and potential
error associated with eluent preparation.
References
1.Thermo Scientific Application Note 258:
Determination of Tetrafluoroborate, Perchlorate, and
Hexafluorophosphate in a Simulated Electrolyte Sample
from Lithium Ion Battery Production. Sunnyvale, CA,
2010. [Online] www.dionex.com/en-us/webdocs/
88116-AN258-IC-Lithium-Battery-AN70399_E.pdf
(accessed Apr. 5, 2013).
2.Doh, C.; Lee, J.; Lee, D.; Jin, B.; Moon, S. The
Quantitative Analysis of the Dissolved Manganese in
the Electrolyte of Li/LiMn2O4 Cell Using by Ion
Chromatography. Bull. Korean Chem. Soc. 2009,
30 (10), 2429–2432.
1
0
-0.1
0
1
3
5
7
Minutes
9
AN70444_E 08/16S
15
Table 3. Sample and spiked sample results.
Injection No.
Amount in
Sample
(mg/L)
Amount in Spiked Sample,
Spiked Conc 0.1 mg/L
(mg/L)
1
ND
0.1030
2
ND
0.1034
3
ND
0.1033
4
ND
0.1034
5
ND
0.1033
Average
ND
0.1033
RSD (%)
—
0.15
Recovery (%)
—
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Figure 3. Overlay of chromatograms of unspiked and spiked samples.
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Appli cat i on N ote 1 0 5 3
Sample Analysis
An electrolyte sample was simulated as described in the
Sample Preparation section and diluted 1 to 50 with DI
water. Five sample injections were made and, as expected,
no manganese was found in the simulated sample. A
sample was then prepared to simulate manganese cathode
dissolution in the electrolyte. This simulated sample had a
manganese concentration of 0.1 mg/L after dilution.
Five injections of the diluted spiked simulated sample
were made to quantify manganese. The measured
concentrations were then compared to the prepared
concentration. This analysis yielded a manganese recovery
of 103% with an RSD of 0.15% (Table 3).